He studied law at Göttingen, graduated in 1816, and took his seat as Assessor in the judicial chamber of the board of government (Regierungskollegium) at Kassel, of which his father Johann Hassenpflug was also a member, in 1821 he was nominated by the new elector, William II, fustisrat (councillor of justice); in 1832 he became Ministerialrat and reporter (Referent) to the ministry of Hesse-Kassel, and in May of the same year was appointed successively minister of justice and of the interior.
Hassenpfiug by training and tradition was a strait-laced official; he was also a first-rate lawyer, and his naturally arbitrary temper had from the first displayed itself in an attitude of overbearing independence towards his colleagues and even towards the elector.
[1] The story of the constitutional deadlock that resulted belongs to the history of Hesse-Kassel and Germany; so far as Hassenpflug himself was concerned, it made him, more even than Metternich, the Mephistopheles of the Reaction to the German people.
[1] With somewhat indecent haste (the appeal had not been heard) he was now summoned by the elector of Hesse once more to the head of the government, and he immediately threw himself again with zeal into the struggle against the constitution.
He soon found, however, that the opinion of all classes, including the army, was solidly against him, and he decided to risk all on an alliance with the reviving fortunes of Austria, which was steadily working for the restoration of the status quo overthrown by the Revolutions of 1848.
[1] On his advice the elector seceded, from the Northern Union established by Prussia and, on September 13, committed the folly of flying secretly from Hesse with his minister.